how to study the brain Flashcards
What is a stroke?
-Causes motor language impairments
-Depends on which brain region is damaged
What is Alzheimer’s disease?
-Damage starts in medial temporal (hippocampus)
What is Parkinsons disease?
-Degeneration of neuron’s in substantial nigra (midbrain)
Describe the case of Patient Leborgne
-Suffered stroke
-Damage to left side of frontal cortex (Broca’s area)
-Lack of speech, could only say ‘tan’
Describe the case of Phineas Gage
-Metal rod through frontal cortex
-Behaviour changed and became impulsive
Is hippocampus both necessary and efficient?
-Hippocampus is necessary for spatial and declarative memory but it isn’t sufficient
(R) What is a lesion?
-Wound or injury
What are the 6 methods used to study the brain?
-Behavioural studies
-Manipulations of brain functions
-Neuroanatomy and histology
-Electrophysiology
-Imaging (MRI and PET)
-Computational models/brain based devices
Describe the use of manipulations of brain functions
-Neurological patients/ones with brain damage, if you know which part is damaged then you can figure out the role
-Conducted more on animals to be more ethical
Describe the use of neuroanatomy and histology
-Connection to other brain sites
Describe the use of electrophysiology
-Listen to electrical activity of neurons
Describe the use of imaging (MRI and PET)
-Non-invasive methods
Describe the use of computational models/brain based devices
-Once we know how a brain region links to a psychological process, we can build a model on how a brain circuit links to functions
Describe in detail what happened in the case of Patient H.M.
-Had his hippocampus removed to stop epileptic seizures
-Used behavioural and cognitive analysis
-Found that he had impairments in spatial and declarative memory
What is spatial memory?
-Memory of directions and locations
-He couldn’t form new ones
What is declarative memory?
-Memory that we can recollect
-Includes semantic and episodic memory
(R) Describe stereotaxic surgery
-Ability to locate objects within a space
-Keeps animals head in position and an arm that moves an electrode through measured distances in all 3 axes of space
What are optogentics?
-Manipulating specific neurons in the brain so that they become light sensitive
-Shining a light means you can either activate or inhibit neurons
What is Trans-cranial magnetic stimulation (TMS)?
-Disrupt electrical activity but inducing magnetic field on the surface of the brain
What occurs during neuronal tract tracing?
-Tracer is injected into 1 brain region
-Travels in direction of action potential
What happens in diffusion magnetic resonance imaging?
-Highlight white fibre tracts
How do you record the electrical activity of the brain?
-Planting electrodes into the brain region to record specific electrical signals from neurons
-Each neuron has different firing rates
-Local field potential (LFP) recordings, where you record electrical potentials generated by neurons known as field potentials
How is water maze used to look at learning deficits after hippocampal lesions in rats?
-Rats don’t have declarative memory but do have spatial memory
-Spatial cues placed to find the correct location
-Get faster each time
-Remove it and track their pathway
What are invasive single-unit and LFP recordings?
-Only conducted in rare cases for pre-surgical evaluation of epilepsy patients
-Neurologist would plant electrodes to figure out where the seizure is coming from, so that the surgery is conducted on the smallest area needed
What is a surface EEG?
-Spontaneous and event-related (evoked)
-Record electrical activity generated by the brain by putting electrodes on the surface of the brain
-Can be used to diagnose epilepsy
What is magnetoencephalography?
-Conducted with neuromagnetometers
-Measures the small magnetic-field changes that arise from the electrical voltage changes due to brain activity
-Better spatial resolution than EEG (<1cm)
-Require a large machine that is very expensive and difficult to do on children
What is magnetic resonance imaging (MRI)?
-Images are generated from MR signal
-Nuclei of spinning hydrogen atoms align with magnetic field
-These are aligned by a strong magnetic field
-Excited by magnetic pulse
-Doesn’t use x-rays
Describe the use of structural MRI of the brain
-Non-invasive imaging of brain structure
-Based on MRI contrast between different tissue types due to different densities of H nuclei
-Would have been used on H.M to confirm which area is damaged
Describe the use of functional MRI of the brain
-Non-invasive imaging of brain ‘activity’ based on MR signal changes
-Associated with metabolic and cerebral-blood-flow changes
-Most common method is based on changes in Blood-Oxygen-Level-Dependent (BOLD) MR signal
-Best spatial resolution
Is the hippocampus both necessary and efficient?
-Just a correlation
-Doesn’t tell you that the hippocampus is necessary or sufficient for memory
What is positron emission tomography (PET)?
-Involves injection of radioactive tracers that resemble compounds of biological interest
-Uses dedicated tracers around the head
-Tracers can be followed in brain e.g. to monitor metabolic activation
-Tend to use MRI more now
-Poor spatial resolution and costly
How can PET imaging be used to monitor brain activity and chemical neurotransmission?
-Can cause changes in Parkinson’s disease
-Less DAT in striatum - reflects degeneration of dopaminergic fibres that express this transporter at terminals
-More binding of dopamine receptor specific tracers - reflects less dopamine release that could displace tracer from receptor
-Some regions are hypo, others hyperactive
